Research described in this proposal involves the synthesis and characterization of mononuclear iron(IV)-oxo (Fe(IV)=O) complexes that mimic high-valent iron centers proposed to be key oxidants for certain non-heme (NH) iron enzymes that are present in organisms ranging from bacteria to humans. While current research has afforded the isolation and characterization of a number of synthetic, mononuclear Fe(IV)=O complexes, these model systems differ from their biological counterparts in terms of Fe coordination environment and spin state. Accordingly, ligand scaffolds containing carboxylate and amide functionalities, which provide a closer mimic to the active sites of NH iron enzymes, will be used to support Fe(IV)=O species. The complexes generated for this study will be characterized using electronic absorption, Mossbauer and X-ray absorption spectroscopies, and the reactivities of these complexes with respect to organic substrates will be examined. The results of this combined synthetic and spectroscopic approach should offer valuable insight into the electron structures and reactivities of intermediates in NH iron enzymes, allowing for a better understanding of the oxygen-iron chemistry used by nature to perform oxidative transformations.